1. Field of the Invention
The present invention relates to a system for pretreating wheat to be floured to remove pericarp from each wheat grain, to thereby expose an endosperm part thereof. The present invention relates also to a process for flouring wheat and a system for carrying out the process.
The term "wheat" used throughout the description of the specification and the appended claims is intended to include "wheat" or "rye".
2. Related Art Statement
In general, a pretreatment of wheat to be floured includes, in addition to the removal of dusts, impurities, pebbles and the like, drying or humidifying the wheat temporarily stored in a storage bin, silo or the like to temper the wheat of the same lot so as to have a uniform moisture content, and increasing the moisture content of the wheat by 0.25%-0.5% 30 minutes to 2 hours prior to a milling treatment thereof by means of a rolling machine, to bring the moisture content of a gluten part of each wheat grain to a level slightly higher than that of an endosperm part thereof so that separation of the gluten part from the endosperm part is facilitated and the gluten part is prevented from being finely pulverized.
Subsequently, the wheat is milled by the rolling machine to form flour. It is impossible to completely remove the endosperm part from each wheat grain by only one pass of the wheat through the rolling machine, and it is usually necessary to pass the wheat through the rolling machine four to seven times. The first pass is referred to as a first breaking and the succeeding passes are referred to as a second breaking, a third breaking, and so on. The material milled at each breaking is sorted by a screen such that the milled material remaining on the screen is fed to the subsequent breaking, while the milled material having passed through the screen is further pulverized.
Based on such characteristics that the affection of the pressure milling by the rolls to the endosperm part of each wheat grain at each breaking is slightly higher than that to the pericarp of the wheat grain so that the endosperm part of each wheat grain is brought to a slightly finer particulate material, the milled material is sorted by the screen to collect the endosperm parts as flour. In this manner, the milled material is sorted by the screen at each breaking and the milled material remaining on the screen is successively subjected to the succeeding breakings, to thereby extract the endosperm parts as the flour.
The percentage of the pericarp of each wheat grain to the endosperm part thereof is in general 12 to 17%, although the composition of the wheat differs depending upon the kind of the wheat or the place of production, and although the value of the percentage differs depending upon the classification as to which of the pericarp or the endosperm part of each wheat grain the aleuron layer at the boundary between the pericarp and the endosperm part belongs. Accordingly, should the pericarp and endosperm part of each wheat grain be completely separated from each other, the yield of the wheat would be 83-88%. However, the average yield by the conventional wheat flouring processes and systems is only 73-78%.
In order to improve the yield of wheat flour of a high quality, it is necessary to strip and remove the endosperm part of each wheat grain out of the pericarp thereof while maintaining the endosperm part to a coarse particle as far as possible. In addition, in order to strip and remove the endosperm part from the pericarp while maintaining the endosperm part to the coarse particle, it is desirable to treat the wheat with a less number of breakings, but third to fourth breakings are usually required. However, as the milled material broken at the breaking is sorted by the screens, the particles remaining on the screens are successively milled at the subsequent breaking and it is repeated at the fourth to seventh breakings to strip the endosperm part left adhering to the pericarp from the pericarp, the particle size of the milled material is gradually reduced so that the gluten part and the endosperm part of each wheat grain resemble each other in property or characteristic and the percentage is increased by which the pericarp particles are mixed in particles to be extracted as the endosperm parts with the pericarp particles having the same size as the particles to be extracted, thereby deteriorating the quality of the wheat flour. Accordingly, in order to produce a high quality wheat flour at a high yield, a skilled technique is required for the determination of the surface configuration of the rolls used in the breakings, the setting of the optimum gap between the rolls which is optimum for each breaking and the setting of the operating conditions of the rolls.
As described above, it is impossible for the conventional flouring techniques to completely separate the peicarp and the endosperm part of wheat grain from each other. In addition, should the yield of the flouring be increased, the quality of the wheat flour would be deteriorated and, inversely, should the quality be improved, the yield would be reduced.
Japanese patent publication No. 29-7620 published for opposition purposes on Nov. 29, 1954 discloses a friction type wheat polishing machine which comprises an auger including one or more first blade fixedly mounted on a shaft for forcibly delivering wheat grains helically, a pair of second blades fixedly mounted on the shaft for successively divide the wheat grain flow forcibly delivered helically, into discrete mass portions, and a third blade mounted on the shaft for mixing the divided mass portions with each other.
Japanese patent publication No. 30-7159 published for opposition purposes on Oct. 7, 1955 discloses a wheat polishing system which comprises a friction type wheat polishing machine, an agitating machine for adding water to the wheat grains to be fed to the friction type wheat polishing machine and for mixing the same, and a grinding machine for grinding the wheat grains discharged from the friction type wheat polishing machine.
Japanese patent publication No. 33-64 published for opposition purposes on Jan. 11, 1958 discloses a wheat polishing system which comprises a grinding type wheat polishing machine, a polishing type bran removing machine for polishing wheat grains discharged from the grinding type wheat polishing machine to remove bran from the wheat grains, an agitating machine for agitating wheat grains discharged from the polishing type bran removing machine while adding water to the wheat grains, a friction type wheat polishing machine for polishing wheat grains discharged from the agitating machine, and a polishing type bran removing machine for removing bran from each wheat grain discharged from the friction type wheat polishing machine. The wheat grains discharged from the last polishing type bran removing machine are returned to the first grinding type wheat polishing machine by means of an elevator.
Japanese Utility Model publication No. 32-14752 published for opposition purposes on Nov. 20, 1957 discloses a water adding machine which comprises a water supplying chamber, a nozzle for supplying water to the water supplying chamber, and a pair of agitating blades fixedly secured to a shaft rotatably disposed in the water supplying chamber. As the shaft is rotated, the agitating blades cooperate with an inner surface of a wall defining the water supplying chamber to agitate the wheat grains under friction while water from the nozzle is being supplied thereto.
Applicant is aware of the following U.S. patents which disclose a polishing machine with humidifier. It is to be noted, however, that these U.S. patents are directed to the treatment of rice, but not wheat:
U.S. Pat. No. 4,133,257 issued on Jan. 9, 1979 to Toshihiko Satake; PA0 U.S. Pat. No. 4,148,251 issued on Apr. 10, 1979 to Toshihiko Satake; PA0 U.S. Pat. No. 4,155,295 issued on May 22, 1979 to Toshihiko Satake; PA0 U.S. Pat. No. 4,323,006 issued on Apr. 6, 1982 to Toshihiko Satake; and PA0 U.S. Pat. No. 4,488,481 issued on Dec. 18, 1984 to Toshihiko Satake.